\begin{tikzpicture}[>=Stealth,
    every node/.style={fill=white, inner sep=1pt, outer sep=3pt},
]
    \pgfmathsetmacro{\factor}{0.3}
    \pgfmathsetmacro{\a}{5.8 * \factor}
    \pgfmathsetmacro{\e}{\a * 1.6}
    \pgfmathsetmacro{\jiaoa}{asin(\a/\e)}
    \pgfmathsetmacro{\b}{cos(\jiaoa) * \e}
    \pgfmathsetmacro{\r}{0.5}

    \coordinate (A) at (0, 0);
    \coordinate (B) at (\b ,\a);
    \coordinate (C) at ($(B) + (9.8 * \factor, 0)$);
    \coordinate (D) at (2 * \b + 9.8 * \factor, 0);

    \fill [draw, thick, pattern = dots]
            (A) node [below] {$A$}
         -- (B) node [above left] {$B$} node [midway, above, rotate=\jiaoa] {$i = 1:1.6$}
         -- (C) node [above right] {$C$}
         -- (D) node [below] {$D$}
         -- cycle;
    \draw (A)  + (0:\r) arc (0:\jiaoa:\r) node [pos=0.8, right] {$\alpha$};
    \draw [<->, transform canvas = {yshift=0.5em}] (B) to [xianduan] node [above] {$9.8$m} (C);
    \draw [<->, transform canvas = {xshift=0.5em}] (D) to [xianduan={above=\b cm + 0.5em}] node [above, rotate=90] {$5.8$m} ($(D) + (0, \a)$);
\end{tikzpicture}

